In a case of the prior art, as disclosed in the following patent document, there is a structural arrangement where on a side wall of a cylinder block is provided a by-pass passage to introduce the cooling water discharged from a water jacket into a water pump.
Unexamined Patent Publication No. 2002-364360
In the above-described known structure, it is necessary to provide the by-pass passage on the outside of reinforcement ribs formed over the side wall of the cylinder block, so that the projecting size out of the side wall comes to be larger corresponding to the by-pass passage. This means a drawback that an external form of an internal combustion engine comes to be larger, so that the capability of the engine for installation on vehicles is reduced.
Further, when a cylinder head is fastened through bolts to a cylinder block, according to a large fastening force of the bolts against the cylinder block there is generated a large working force to pull up the cylinder block in the direction to the cylinder head. Because of this working force, there arises the externally oriented deformation in the vicinity of the bottom of the water jacket formed on the periphery of cylinder bores, so that inferior roundness of the cylinder bores occurs. As a result, there are such problems as increase of the frictional loss between the cylinder bores and the pistons sliding therein, output power decrease of internal combustion engines, inferior sealing performance of piston rings, increase of blow-bye gas, etc.
In view of the above-described conventional problems, it is an object of the present invention to provide a cooling water passage structure of internal combustion engines which enables the internal combustion engine to be reduced in weight without enlarging the external form thereof and enables the deformation of the cylinder bore to be suppressed.
According to an aspect of the present invention, there is provided a cooling water passage structure of internal combustion engines, comprising: a water jacket for flowing of cooling water provided on the peripheries of a plurality of cylinder bores; and a lateral suction passage integrally formed with a side wall of a cylinder block having bolt holes formed for fastening a cylinder head, the lateral suction passage running through by the cylinder bores at a height in the vicinity of the water jacket bottom, and the suction lateral passage arranged on the outside of and perpendicular to the bolt holes.
Thus, the suction lateral passage is formed integrally on the side wall of the cylinder block and outside of the bolt holes, and the suction lateral passage runs through by the plurality of cylinder bores at a height in the vicinity of the water jacket bottom, such that it is arranged perpendicular to the bolt holes. In this way, by disposing the suction lateral passage perpendicular to the bolt tightening direction at the height in the vicinity of the bottom of the water jacket which may be deformed most seriously when the bolts are tightened, the deformation of the cylinder bore due to the bolt tightening can be suppressed excellently. Therefore, the side face rib of the conventional cylinder block can be eliminated, thereby achieving reduction of the internal combustion engine in weight. Further, because the projection of the suction lateral passage outward can be reduced, the external form of the internal combustion engine can be reduced, thereby improving its loading performance on a vehicle.
According to another aspect of the present invention, a suction vertical passage rising from the cylinder block up to the cylinder head is formed integrally with the rear end side of the suction lateral passage and the top face opening in the cylinder block side of the suction vertical passage and the bottom face opening in the cylinder head side are sealed with a cylinder head gasket at the same time.
Because the suction vertical passage rising from the cylinder block up to the cylinder head is formed integrally with the rear end side of the suction lateral passage and the top face opening in the cylinder block side of the suction vertical passage and the bottom face opening in the cylinder head side are sealed with a cylinder head gasket at the same time, they can be sealed excellently with the cylinder head gaskets, so that the suction vertical passage is formed integrally. Consequently, the stiffness of the cylinder block can be intensified, thereby preventing deformation of the cylinder bore due to the tightening of the bolts.
According to still another aspect of the present invention, an opening communicating with the suction vertical passage and an outlet opening for cooling water which cools the cylinder bores are formed in the rear surface of the cylinder head while a water passage containing a path for connecting the two openings and having an outlet and intake to a heater and an outlet to a radiator is provided so as to cover the rear surface of the cylinder head.
Because the opening communicating with the suction vertical passage and the outlet opening for cooling water which cools the cylinder bores are formed in the rear surface of the cylinder head while the water passage is provided so as to cover the rear surface of the cylinder head, the opening in the rear surface of the cylinder head can be covered excellently by the water passage and further, by installing this water passage, deformation of the cylinder bores in the rear surface at the time of bolt tightening can be suppressed excellently.
According to yet still another aspect of the present invention, the front end side of the suction lateral passage communicates with the water pump provided on the front end side of the cylinder block.
Because the front end side of the suction lateral passage communicates with the water pump provided on the front end side of a cylinder block, by providing the water pump on the front end side of the cylinder block integrally or separately, deformation of the cylinder bores on the front end side at the time of bolt tightening can be suppressed excellently.